A riveting machine for aircraft fabrication fastens together two aircraft parts or elements in which the plane of interface is perpendicular to the machine axis, usually horizontal. The interface plane could also be vertical. Fastening is carried out by first clamping the elements, followed by drilling a hole through the elements and then inserting a fastener. In a C or rectangular frame riveting machine upper and lower head assemblies are positioned in alignment on opposite sides of the work pieces and remain along the same vertical axis.
After drilling, inserting the rivet and fastening the rivet, with desired axial contact, referred to generally as installing the rivet, the opposing head assemblies will back away and the machine will move sideways to the next fastening location, under manual, semi-automatic or automatic CNC control. While the movement of the upper fastening head is relatively uncomplicated because the outer surface of outer part is smooth, or has fewer elements than the inner part, which is often complicated, with stringers, clips and frames which the lower tool can accidentally contact from the side and cause damage to during the sideways movement, as well as damaging the lower tool itself. This occurs if the movement of the tool does not avoid hitting the inner part elements. An additional issue occurs with a hooked or offset inner part structure. The backing away and movement of the lower tool is complicated and often results in undesirable contact. It would hence be desirable to have a system for attaching the lower head assembly so as to prevent damage to both the aircraft element parts and/or the tool itself. It would also be desirable to have a simplified changing system for the lower riveting tool.